Production of metal powders



Dec. 22, 1953 SCHLECHT ETAL ,6

PRODUCTION OF METAL POWDERS Filed OC'C. 21, 1950 CARBONYL VAPO H ATED WALLS INVENTORS: LEO SCHLECHT ERNST OESTREICHER BY I 1 gig? ATT'YS Patented Dec. 22, 1953 UNITED STA ES PAT N j.-*1 v PRODUCTION OF METAL PownEns Leo Schlecht and Ernst Oestreicher, Ludwigs hafe n (Rhine), Germany, assignors to Badische.

Anilm- Ludwigshafen & Soda-Fabrik (Rhine) Bundesrepublik, Germany Aktiengesellschaft, Rheinland Plalz,

Application October 21, 1950, SerialNo. 191,500

Claims priority, application Germany November 4, 1949 4Claims. (ems-0.5)

This invention relates to improvements in the production of metal powders by thermal decomposition of metal carbonyls.

In carrying out this known process, the metal carbonyls, preferably in the vapor phase, are led The degree of separation and sifting of the metal into a chamber which is externally heated to temperatures above the decomposition temperature of the carbonyl, the decomposition of the carbonyl taking place in the hot free space of the chamber substantially at a distance from the hot walls of the chamber. generally obtained a metal powder of high purity and some carbon-content which is composed of particles of different sizes. Since, however, for many purposes a definite size of particles is de- In this way there is powder can be influenced by the amount of gas led in. When it is desired to separate from the powder only the finest particles, at smaller amount is generally employed. If, on the other hand, it is important to separate the coarsest particles from the powder, the bulk of the powder is blown "from the decomposition chamber, by means of a powerful current of gas introduced at the bottom of the decomposition chamber,

; into the adjacent separation or sifting apparatus.

The gases may be led in at such a low temperature that they efiect a cooling of the metal sired, attempts have been made to separate the :1".

undesirable particlesfrom the powder by subsequently subjecting the powder to a wind sifting. During the withdrawal of the powder from the decomposition chamber and its conveyance into the wind sifting plant, loosely agglomerated powder particles which usually deposit on the walls of the decomposition chamber and which have a higher carbon content than the individual, non-agglomerated particles, are in part triturated so that in the subsequent wind sifting these particles with higher carbon content also pass into the fraction obtained by sifting and injuriously affect the uniformity of this fraction.

We have now found that the said drawback drical container I is provided with a carbonyl vapor inlet tube 2 at its top and heating means 3 externally surrounding its side. The bottom can be avoided by leading through the decomposition chamber, during or after the decomposition of the metal carbonyl, a current of gases or vapors, preferably a current of carbon monoxide, and recovering the metal powder entrained by the gases leaving the decomposition chamber. In this way it is possible to retain the original form of the agglomerates of the elementary particles and to recover these structures, which are usually in the form of small sponges or tufts, separately from the non-agglomerated particles of the powder. The separation from the gases may be effected in a plurality of stages, for example by means of several, consecutively arranged filters, deflecting or bafile plates or the like, and in this way' a, plurality of fractions of particles of definite sizes may be obtained.

The simplest procedure is to carry out the carbonyl decomposition in an elongated cylindrical container arranged vertically, and to lead in the gases axially at the bottom of the container. By providing a conical cover over the opening of the upwardly directed inlet pipe at desired direction, for example obliquely downwards, can be imparted to the current of gas.

of the container I is constructed to provide conical portions 4 and f5, and the lower conical portion 5 is provided with a valve 6 or the like, through which metal powder is withdrawn.

A gas inlet tube 1 leading from a source of gas, such as carbon monoxide, enters the bottom section of the container I through the wall of the upper conical portion 4 and extends to the axis of the container, where it is turned upwardly, in line with the axis. Spaced above the open end of the gas inlet tube 1 within the container and adjacent the tube end is a conical cover 8, arranged with its apex pointing upwardly, to deflect the gas entering through the tube 1 obliquely downwards. A gas exit tube 9 is connected to the upper conical portion t ofthe container I and communicates with the interior of the container. The exit tube 9 is connected at its other end to a separator I U, which includes a vertically arranged cylindrical collecting chamber II, a valve l2 or the like at the lower end of the chamber ll through which metal powder is withdrawn, an enlarged chamber I 3 at the upper end of the collecting chamber H which encloses a filter I 4, and a filtered gas exit tube 15 at the upper end of the enlarged chamber l3.

In operation according. to the above-described procedures, metal carbonyl vapor is passed through the vapor, inlet tube 2 and into the container l, maintame'd above the decomposition temperature of the carbonyl by the heating means 3. As decomposition progresses, metal powder forms and falls and is carried downtrained in the gas. The gas andentrainedpowder leave the container through the exit tube. 9 and pass into the separator Hi. In the separa tor, powder is removed from the gas by the filter I 4 and is collected in the collecting chamber H, from which it is withdrawn as desired through the valve 1:2. The filtered zgas leaves the separator through the exit :tube 6125. Meanwhile, coarser metal powder which is not entrained in the gas collects in the lower conical portion 5 of the container I, from which it is removed through the valve 6.

The following example will further illustrate the invention but the invention is not limited to this example.

In the'decoinposition ofiron carbonyl with an addition of some ammonia in an externally heated cylindrical container having an internal diameter of "1 metre and .a height of '5 metres. 56% 'of the total amount'of. iron powder formed by the decomposition "separate at the bottom of the container whileth'e remaining 44 are entrainedin'to"anadjacent laterally arranged filter by the carbon monoxide formed ,by the decomposition and leaving the container. The iron powder withdrawn from'the bottom of the decomposition container 'contains 0.83% of carbonandithat' collected in the filter contains 059% o'fcarbon. Bywind sifting of thepowder withdrawn from the 'bottom in ;a current of nitrogen, -a "finest fraction is obtained having a carbon content d *0262 =If,on the other Phand'inthe same decomposition container operated under the same conditions, carbon monoxide is led, in, axially at the bottom, the fraction of :powder :in the laterally arranged filter is "increased 'from4l4% to 58% to the gas current an obliquely downward direction, Soas to entrain a portion of the metal powder formed in said. f ee. space, leading said current of gas out of said container to a solids separator, and separating from the gas the metal powder entrained by the current.

2. In the process of producing metal powders i by thermal decomposition of metal carbonylsin the hot freejspace of an elongated vertical cylindrical container the step which comprises separating .a fraction of powder characterized by low carbon content by leading a current of carbon monoxide gas through the said container While introducing the gas axially at the bottom "andimparting to the gas current an obliquely downward direction, so as to entrain a portion of the metal powder formed in said free space, leading said current of gas out of said container to a solids separator, and separating from the gas the metal powder entrained by thecurrent.

3. In the process of producing metal powders by thermal decomposition of metal carbonyls in the hot free space of a heated container the step which comprises separating .a fraction of powder characterized hy:low-c.ar.b0n content by leading a current :of gas through the container at such a temperature that 'a simultaneous cooling of the metal powderandlcarbon monoxide formed by the decomposition is effected, 'While introducing ="the .gas axially at the bottom and imparting to the gas current an'ololiquely downward direction, so as'toaentrain .aportion of the metalpowder formedin said free space, leading said current of .gas out-of ,said oontainer to a solids separator, and separating from the gas the-metal powder entrained by the current.

14. In theaprocessof producing metalpowders by thermal decomposition =.of metal carhonyls in thezhotiree spaceoian elongated vertical cylind-rical container the step which vcon'iprises separating aifractionflofipowdercharacterized by low cai'boneontent by leadings-a current of carbon monoxide through the .said container axially from its 'BbOliztOIn ;at such a temperature that a simultaneous cooling .of zthe metal powder and carbonmonoxide formed by the decomposition isieffected, while imparting to the gas current an obliquely downward directiomso as to entrain a portion of the; metal .zpowdertormed in said 'free with the samecarbon content of.0.59%. "Inthis way 'theproportion'of iron powder with the 1031',

est'car'bon' contentis increased by about 30%.

What we cl'aimis: I 1. In the process of producing :metal powders by thermal decomposition "of metal ,carbonyls in V space, leadingisaid current of gas out of said container to a solids separator, and separating from theugas -the metal powder entrained by'the current.

SCHIL-ECHT.

. ERNST .OES'IREICI IER.

References-Gited in the-file of thispatent UNI'IED STATES PA'I'ENTS Number Name Date 13%;732 s h cht t al- Dec- 5, 1931 7, 61 iHatch l--,.-. -1Scl i1. 20,1932 118935313 Saint-Jacques Jan. 10,1933 $389,701 Truesdaie Nov. 2'7, 195115 2,4-601546 ,Stephanoff .7 Feb. '1, i!) 

1. IN A PROCESS OF PRODUCING METAL POWDERS BY THERMAL DECOMPOSITION OF METAL CARBONYLS IN THE HOT FREE SPACE OF AN ELONGATED VERTICAL CYLINDRICAL CONTAINER THE STEP WHICH COMPRISES SEPARATING A FRACTION OF POWDER CHARACTERIZED BY LOW CARBON CONTENT BY LEADING A CURRENT OF GAS THROUGH THE SAID CONTAINER WHILE INTRODUCING THE GAS AXIALLY AT THE BOTTOM AND IMPARTING TO THE GAS CURRENT AN OBLIQUELY DOWNWARD DIRECTION, SO AS TO ENTRAIN A PORTION OF THE METAL POWER FORMED IN SAID CONTAINER TO A SOLIDS CURRENT OF GAS OUT OF SAID CONTAINER TO A SOLIDS SEPARATOR, AND SEPARATING FROM THE GAS THE METAL POWDER ENTRAINED BY THE CURRENT. 